High-frequency superregenerative apparatus



May 20, 1952 w. w. HANSEN ETAL 2,596,996

HIGII-FREQUENCY SUPERREGENERATIVE APPARATUS Original Filed July 2, 1946 2 SHEETS-SHEET 1 ATTORNEY May 20, 1952 w. w. HANSEN ET A1. 2,596,996

HIGH-FREQUENCY SUPERREGENERATIVE PPARATUS original Filed July 2. 194e 2 SHEETS- SHEET 2 ATTO RN EY Patented May 20, 1952 UNITED STATES NT @FFI'CE HIGH-FREQUENCY SUPERREGENERATIVE APPARATUS William W. Hansen,

University,

F. Varian, Menlo deceased, late of Stanfordr by Olive D. Ross, executrix, Palo Alto, Russell H. Varian,

Stanford, and Sigurd Park, Calif., assignors to The Board of Trustees of The Leland Stanford Junior Universit Stanford University, Calif.

Continuation of abandoned application Serial No.` 681,096, July 2, 1946, which is a division of application Serial No. 218,064, July 8, 1938, now Patent No. 2,406,370, dated August 27, 1946. This application July 15, 1950, Serial N o. 174,028

Application Serial No. 516,012, filed December 29,

1943 (Patent No. 2,406,371), is also a division of said application Serial No. 218,064.

The principal object 'of the present invention is to provide a novel electronic apparatus adapted for receiving or detecting high frequency signals.

Another object of thepresent invention lies in the production of improved superregenerative receivers for high frequencies, and particularly such receivers operating on the velocity-modulation principle.

A still further object of the invention is to produce methods and means for detecting objects at a distance by the alternate transmission and reception of radio waves intercepted by such objects or by the use of superregenerative apparatus.

Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In thedrawings,

Fig. l is a longitudinal cross-sectional view and schematic circuit diagram of a preferred embodiment of the present invention, and

Fig. 2 is a similar view of another form of the invention.

In Fig. 1, there are shown two resonant circuit members or cavity resonators I and 2 of the type disclosed in U. S. Patent No. 2,242,249, issued May 20, 1941, on application Serial No. 214,452 which was filed June 18, 1938. Resonators I and 2 and their` associated apparatus comprise' two intercoupled velocity-grouped electronic circuit means, the principles of operation of which are described in U. S. Patent No. 2,242,275, issued May 20, 1941, on application Serial No. 168,355 which was filed October 11, 1937. An electron emitter 5, such as an activated-oxide surface heated by a filament 6, is connected with a battery 'I for accelerating the electrons from emitter 5 into the resonator system. Resonator I is provided with a pair of spaced grids 8 and 9 in the path of these electrons. Resonator 2 has a pair of spaced grids I4 and I5also in the path of the electron stream. Resonator YI is also shown provided with a cou- 18 Claimns.v (Cl. Z50-20) pling loop i0 and a connected antenna |02. An opening 20 in resonator I may beused with or in lieu of antenna |02 for receiving energy. A coupling loop I6 in resonator 2 is coupled t0 a similar loop i I in resonator I by coupling concentric transmission line I3, whereby the resonators and 2 are electromagnetcally coupled together. Resonator 2 is provided with a coupling loop IOI coupled to an antenna ID3. Antenna |03 or opening 20I in resonator 2 (or both) may be used for radiating electromagnetic energy from reso nator 2.

Beyond resonator 2 there is shown a detectorV 24 are connected to a push-pull transformer 26' which delivers its output to a telephone or other receiver 21.

Between the emitter 5 and the grid 8 there is located a control grid 37 connected to an oscillator 39 of comparatively low frequency. Be-v tween resonators I and 2 there is a tubular electrode 38 connected to a second low frequency oscillator 39.

In the operation of this system, the electrons of the beam in passing through the grids 8 and 9 of resonant circuit member I are alternately accelerated and decelerated,as explained in Patent'Y No. 2,242,275. As a result of the changes in velocities of the electrons of the beamV and of their subsequent passage through the iield-free drift space between grids 9 and I4, they arrive at the grid I4 of resonator 2 in groups or bunches distributed in time at the frequency of oscillation of the resonator system. Resonator I may there# fore be termed an electron-grouping circuit. Energy is transferred from the electrons to the electromagnetic field within resonator 2, and this resonator 2 is thereby excited to a state of oscillation and may be termed an electron-beamexcited circuit. Some of the energy of the oscillation frequency is transmitted from resonator 2 to resonator I through feed-back coupling loop i0, transmission line I3 and coupling loop II. Thus, the resonator I is maintained in a state of A second plate 24 is placed as oscillation, and the electron beam is accordingly continuously acted upon and bunched.

Assuming that a modulated carrier frequency is received by resonator I through either hole 20 or antenna |32, or both, the electrons of the beam are velocity-modulated and grouped in the manner discussed above. These electrons then travel through grids I4 and I5 and encounter grids 2| and 22. The electrons emerging from grid I5 have varying velocities, depending upon the amplitude of oscillation in the resonators and 2. Some of the electrons pass through grids 2| and 22 and hit plate 23. Other electrons (that is, the slower ones) are reflected from grids 2| and 22 to plate 24, in a manner which will now be described more fully. The two grids 2| and 22 are parallel and close together. A potential difference is established between grids 2| and 22 by the battery 30, maintaining grid 22 negative with respect to grid 2|. The resultant eld between grids 2| and 22 acts like a flat mirror so far as the slower electrons leaving grid I5 are concerned. These slower electrons, on entering the field between grids 2| and 22, have their motion opposed by this iield and are deflected toward plate 24. The faster electrons are deflected or refracted somewhat, but nevertheless penetrate the eld between grids 2| and 22 yand hit plate 23. The slower electrons are not able to penetrate this field, but bounce to the left, as in ordinary optical reflection, to be received by plate 24.

In the structure comprising resonators I and 2, all the electrons leaving the grid I5 have substantially the same Velocity when the system is not oscillating. As the amplitude of oscillation increases, the electrons vary in velocity. For larger amplitudes of oscillation, the extremes of electron velocity are more widely separated. Thus the number of electrons flowing to plates 23 or 24 corresponds to the amplitude of oscillation of the resonators. The potential difference between grids 2| and 22 is adjusted either so that most of the electrons are reflected toward plate 24 or so that most of them are permitted to pass to the plate 23. The precise difference of potential between grids 2| and 22 giving the most sensitive or the most ecient detector action, as may be preferred, can be found by experimental adjustment of battery 30. The detector characteristic of this system is analogous nary vacuum tube circuits.

Since practically all the electrons emerging from grid I5 eventually strike either plate 23 or plate 24, any increase in current reaching one of these plates is accompanied by a decrease in current reaching the other plate. Hence, the current produced by electrons reaching plate 23 is one hundred eighty electrical degrees out of phase with the current produced by electrons reaching plate 24. Accordingly, the currents from plates 23 and 24 are appropriate to the operation of any push-pull apparatus usually used with push-pull detectors, such as transformer 26 and receiver or other utilization device 21.

The grid 31, the electrode 38 and the oscillators 39 and 39 are used to control the operation of the system for starting and stopping or Varying the amplitude of oscillation. As is described in U. S. Patent No. 2,281,935, issued May 5, 1942, on application Serial No. 326,150 which was filed March 27, 1940, an alternating Voltage applied to grid 31 or to electrode 38 accomplished amplitude modulation of the amplitude of oscillation of resonators and 2. If this voltage is made suiciently high, the oscillation of the system to that found in ordil can be stopped during part of every modulating cycle. The frequency of oscillators 33 and 39 may be of any desired value up to about 10'I cycles per second, or even higher if the frequency of the resonators I and 2 is higher than l()8 or 109 cycles per second. Ordinarily, the frequencies of oscillators 33 and 39' will be well within the frequency range yof ordinary triode oscillators. Either grid 31 or electrode 38 or both may be used. Ordinarily, only one will be required, although in some instances it will be convenient to use both operating at the same or different frequencies.

The assemblage shown in Fig. 1 will operate alternately as a simple velocity modulation appara'tus for transmission of radio waves and for the detection thereof. It will also operate as a superregenerative receiver. For best results the assemblage is placed in a suitable parabolic or other reflector as described in application Serial No. 185,382, led January 17, 1938, which matured into U. S. Patent 2,415,094 on February 4, 1947. Also, a shield d is ordinarily used between the transmitter antenna |03 and the receiver antenna |32. v

Either gri/d 31 or tube 38 is used with its corresponding oscillator 39 or 39 adjusted so that during part of the low frequency oscillation cycle of oscillator 39 or 39 the resonator system will oscillate strongly and during another part of the cycle it will oscillate weakly. It is characteristic of Velocity modulation apparatus of the present type, one form of which is called the klystron," that it is comparatively sensitive to the effects of incoming signals when oscillating weakly but relatively insensitive when oscillating strongly. For effective radiation strong oscillations are desired. The adjustment of voltage on grid 31 or tube 38, whichever is used, is made such as may be required to nearly stop oscillations during part of each low frequency cycle of oscillator 39 or 39. During other parts of the cycle the system can operate with less restriction and at some parts of the cycle without any restriction.

Thus, the system transmits pulses of high frequency radiation, the pulses being at the frequency of the low frequency oscillators 39 or 33', and in between pulses of radiation the system is prepared to receive radiation. If the transmitted radiation encounters a suitable reflecting body or object some radiation will be returned to the system where it will be received and detected during the reception part of the low frequency cycle. In this mode of operation, the system operates alternately as a detector and as an oscillator.

Furthermore, it may operate as a superregenerative detector if adjusted properly. During superregenerative operation, oscillator 39 or 39' is adjusted so that, during part of its low frequency oscillation cycle, the resonator system will gain oscillatory strength, and during another part of the cycle, the oscillations will be made to die down; that is, will be quenched The adjustment of voltage on grid 31 or electrode 38, whichever is used, is such as required to nearly or completely stop oscillations during part of each low frequency cycle. During other parts of the cycle, the system operates in an oscillating condition. The conditions for superregeneration are, in general, fullled if the oscillator is allowed repeatedly to build up self-sustained oscillations for a period shorter than the time required for the oscillator to reach full oscillation and then is stopped. The amplitude reached before oscillation is stopped is then sensitive to incoming signals. This amplitude hence corresponds to the modulation envelopeof ther'eceived signal. The amplitude. of oscillation-of the resonators-iis detected by the detector arrangement already'described, so that the output signal supplied to receiver 21 will be the modulation envelope of the .signal received by antenna |02 or through hole'20.

The above-described .use of the application.- as a superregenerative detector: for modulated 'waves does not require the use of antenna |03'orzopening so that these features of Fig. 1 may be omitted when usingthe apparatus solely for reception of modulated waves.

The present apparatus may be used as an object-detecting system in another manner. For -such a system, antenna |03 or opening 20|. (or both) are `also used. As described above, the combination of. the-two resonators and 2, and their'feedback coupling I3 serves as an oscillator, and the oscillations thereby produced may be radiated 'by the antenna |03 or the opening 20| vor both toward a distant object whose presence and (as will be seen) velocity are to be determined; l

-Radiation leaving the apparatus by wayof antenna |03 and opening 20| will be returned by reflection from the distant object and will be received by antenna |02 and opening 20|. The returned radiation will produce an electromagnetic field in resonator whose phase relation relative to the 'normal bunching eld therein is determined by the distance-to .thedistant object. This received signal will combine `with the steady oscillation vof the system .and lwill add to or subtract from the amplitude of the steady oscillation dependingy upon the phase of the received signal relative 'to the oscillation of the system.

Since variationin distance to the distant object'will cause a corresponding variation-in the phase ofthe received signal, the observed result of the action of the system will be to produce an undulating intensity of amplitude of oscillation in the resonator as the distance` of the `apparatus to the distant `object varies. Byv the action of the detector described above, the signal pro-I duced in receiver. 21 will also be of corresponding undulatingA intensity, and will have a frequency corresponding to the velocity of 'approach or recession of the distant object from the apparatus;

In operating in this manner, the system operates as aV transmitter during the unquenched portions of the quenching cycle. The resultant vamplitude of oscillation of the resonator system depends' upon the distance to the distant object, and this amplitude will be periodically varied as the distance to the distant obj ect 'correspondingly varies. The .frequency of ythe signal heard in receiver 21 will, of course, be proportional to the velocity of recession or approach of the object detected. In this way the system operates to detect the presence of moving objects and also indicates the velocity of the distant object toward or away from the apparatus.

Fig. 2 shows another form of the present invention. In Fig. 2, three resonant circuit members or resonators 1|, 12 and 13 are shown mutually spaced and centered on the same axis. A beam of electrons is projected from emitter 5 through resonators 1| and 12 in succession, and a second beam of Velectron is projected from .a second emitter 32 through the resonators 1,3 and 12 in succession. Between the emitter 5 andits vadjacent resonator 1| is a control grid 51 connected to an oscillator 6|. A similar grid 58 is located between emitter 32 and resonator 13, and

is connectedtc ani'oscillator .62.y ,Apa'ir Ofcom- Vductingtubiilar e1ectrodes163-and 64 are vlocated respectively between resonators 1| and112z and between resonators 12 and 13. Electrodes 6.3 and 645' are connected to the respective. ends of. a center-tapped secondary coil.6.5.of..a transformer whose primary winding 66 is vconnectedto* :anoscillator 61.

In Fig. 2, the physical arrangementl issuch that it is not convenient to use the detector shown in Fig. 1. In place thereof, a third beam of electrons is produced by a third electron emitter 5| and is projected through resonatorA 12 transversely to the axis of the system. by Way of grids 52 and 53 in the walls thereof. This beam passes between the faces of resonator 12 containing grids I4 and I5 and leaves resonator 12 through grid 53. Thereafter, the beam is intercepted by 4a plate 54 having an opening 55, and the portion of the beam passing through opening 55 impinges upon a plate 23 to which is connected to receiver 21.

The operation of this transverse-beam detector is described in U. S. Patent No. 2,272,165, wherein it is disclosed that the electron beam Vis deflected vertically with respect to horizontal grids I4 and I5 by the alternating electric eld therebetween. The deflection of the electron beam is a function of the amplitude of oscillation in resonator 12, and the detected signal received from plate 23 by the receiver 21 is also a function of the same amplitude. The plate 54 can be arranged with respect to the transverse electron beam so that, with no oscillation in resonator 12, substantially the entire cross-section of the electron beam will pass through opening 55, or so that practically none of the beam goes through under this condition. In either case, oscillations developed in resonator 12 will cause a variation in the number of electrons passing through opening 55, `such variation being a Afunction of the amplitude of oscillation.

The arrangement of Fig. 2 may be operated as a system which periodically produces strong oscillations forthe purpose of transmitting a strong signal and thereafter has its oscillations damped so that it will act as a sensitive receiver for reflected waves or other modulated received signals. Under this condition of operation, the two electron beams from emitters 5 and 32 are adjusted to have substantially equal eect upon resonator 12. A modulating voltage of any practical frequency is supplied to transformer 6B from oscillator 51 and is thereby impressed iin opposite phase upon electrodes 63 and 64, so that electrode 63 will increase in potential when electrode 54 decreases in potential, and vice versa.

The effect of a variation in the potential of electrode 63 is to change the time of iiight .of electrons in their course from resonator 1| to resonator 12, and also to cause the frequency of oscillation of resonator 12 to vary slightly, an eiect which may be undesired. A corresponding and opposite effect occurs as a result of the opposite variation of the potential of electrode 64. The effects of frequency change due to change of time of Hight of electrons passing. through electrodes S3 and 54 is neutralized by the opposite directions of change of potential of the two electrodes. That is, if the electrode B3 is swung positive with a resultant-I tendency to `increase frequency, the electrode E4 will be simultaneously swung negative and its tendency will be to reduce frequency. The net eiect Will be that the amplitude of oscillation in resonator 1.2 will be varied Awithout; any change in frequency. This feature is claimed in our parent application Serial No. 218,064.

The preferred mode of operation of Fig. 2 is similar to that of operation of Fig. 1, in that the system acts alternately as a transmitter and as a receiver of radio signals. As explained before, the ordinary klystron is a sensitive detector when its amplitude of oscillation i's small, but is less sensitive when the amplitude is large. Accordingly, it can operate either as a detector or as a transmitter satisfactorily by periodically shifting the amplitude from one magnitude to another. This is accomplished in Fig. 2 by the action of either one of oscillators 6| or 62. Either one or the other alone is suiiicient, so if one is used the other may be omitted. Assuming the use of oscillator 62, for example, the electron beam from emitter and the coupling of loops Il and IG between resonators 1| and 12 are adjusted so that, without the assistance of the electron beam from emitter 32, the system oscillates weakly and acts as a sensitive detector. With the electron beam from emitter 32 added at every positive half cycle of oscillator E2, the system is adjusted so that it oscillates vigorously. Then, the oscillator 62 is arranged so that its frequency can be varied as desired by adjusting knob 62', and so that it impresses a potential on grid 58 suiiicient to substantially stop the electron beam from emitter 32 during alternate half cycles of the output of oscillator 62.

In using the device of Fig. 2 as shown trouble may be caused under some circumstances by the electrons that pass clear through the catcher 12, and enter the buncher 1| or 13 opposite their point of origin. In many cases these electrons will have a more or less random distribution in time, and should therefore cause little trouble, but in case they do make trouble, these electrons can be completely removed by setting the two beams from the two bunchers 1| and 13, at a slight angle with respect to each other, or by the use of magnetic or electrostatic deilecting fields in the spaces between the resonators, so that the electrons from one beam do not pass to the opposite buncher but are caught by the walls of the device.

The operation of the system then develops as follows: Energy is radiated by means of coupling loop ||l| and the antenna E03 connected thereto. The radiated energy goes away from the oscillator and if a reecting surface such as a remote object, for example an aircraft, is present at a practical distance from the system, some of the radiated energy is reected back to the system. This reflected and returned energy enters resonator 1| through antenna |02 and is detected by the transverse electron beam from emitter 5|, in the receiver 21. In the use of this system the operation is substantially as described in application Serial No. 185,382, except that there, separate detectors and transmitting oscillators are used. In the use of oscillators and detectors intermittently started and stopped at constant frequency there are, as mentioned in application Serial No. 185,382, alternate regions in the radiation eld from which reflected signals vary from zero to maximum. To avoid dead spaces in the observed space the interrupting frequency is frequency modulated at a lower frequency by additional oscillators 1G and 14' connected to frequency-modulate oscillators 6| and 62, respectively. Arrangements for accomplishing this are shown in application Serial No. 185,382.

Another Way of operating the system shown in Fig. 2 is to use it as a superregenerative detector. 'Ihe modulating voltage impressed on electrodes 63 and 64 is made great enough to stop oscillation in resonator 12 during part of the cycle of the modulating signal. As is well known, a superregenerative receiver is very sensitive to incoming waves during the time when an oscillating state is building up in the system, and, at the same time, the average amplitude of oscillation for radiating purposes may be moderately large. The system thus operates in a manner similar to that of Fig. 1, both as an object detector for moving objects and as a receiver for modulated Waves, the energy being radiated by antennav |03 coupled to resonator 12 by coupling loop |51 and being received by both antennas m2 and |04 coupled respectively to resonators 1I and 13 by respective coupling loops l0 and |05. In this mode of operation, grids 51 and 58 and oscillators 6| and 62 need not be used.

Operation of the system of Fig. 2 as a superregenerative detector may be accomplished in another manner, by using one of the beams for quenching the oscillations normally produced by the other beam. In this mode of operation, electrodes 51, 63 and 64 and their coupled oscillators 6| and B1 may be omitted. For example, the beam from emitter 5 may be adjusted so that, with the beam from emitter 32 cut off, oscillations in resonator 12 build up rapidly but with the beam from emitter 32 added, the oscillations are abruptly stopped.

This is accomplished by adjusting the accelerating voltage supplied by battery 33 for the beam from emitter 32 so that the electron current from emitter 32 enters resonator 12 with its radio-frequency component in phase opposition to the radio-frequency component of the electron current from emitter 5. Oscillator 62 is then adjusted to cut off the beam from emitter 32 each half cycle. This starts and stops oscillations in resonator 12 each quenching cycle, as required for superregenerative operation.

In this mode of operation, the system of Fig. 2 also operates either as a superregenerative detector for modulated Waves or as anl object-detector and velocity for moving objects, as in Fig. l.

In Figs. 1 and 2, if desired, only a single radiating means supplied from either the electron grouping circuit or the electron absorbing circuit may be used both as transmitter and receiver.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained inthe above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. High frequency superregenerative receiving apparatus, comprising means for producing an electron stream, a cavity resonator coupled to said stream and excited by a received Wave, a second cavity resonator coupled to said stream, means for intercoupling said cavity resonators to produce self-sustained regenerative oscillations in said second resonator, means for detecting changes in the amplitude of oscillations of said second resonator, and means for periodically varying the current of said stream at a periodicity less than the time required for said second cavity resonator to build up oscillations therein.

2. `High Ifrequency superregenerative receiving apparatus comprisingmeans for producing Va -stream of free electrons, receiving circuit "means including a cavity resonator connected to receive and responsive to a received wave for varying the velocity of the electrons of said stream, means in the path of said stream for detecting variations in the velocities of the electrons of said stream, an utilization device controlled fromlsaid detectingV means and electrode means between said stream-producing means and said detecting means -for periodically controlling said electron stream `at a periodicity smaller than the time required for said receiving circuit meansto build up oscillations therein.

43. High frequency superregenerative receiving apparatus, comprising means for producing an electron stream, means "excited by a 'received wave for velocity-modulating sai-d stream,1neans for extracting high frequency energy from said stream, means intercoupling saidA extracting means and said modulating means to produce self-sustained regenerative oscillations, Vmeans for detecting changes in the amplitude ofsaid oscillations, and means including an electrode interposed betweeni `said velocity-modulating means andsaid extracting means for periodically controlling said stream to prevent said oscillations at a periodicity less than the time required for said oscillations to build up to full amplitude.

4. High frequency superregenerative receiving apparatus comprising cavity resonator means responsive to a received wave, means for producing oscillations in said resonator means comprising a source of electrons and means for'projecting said electrons in energy-exchanging relation Vto said resonator means, output means responsive to the amplitude of oscillation of said resonator means, and means including an electrode interposed between said cavity resonator means and said output means for periodically quenching said oscillations at a periodicity smaller than .the build-up timeof said 'oscillations in said resonator means, said `quenching means comprising a source of quench oscillations connected to said electrode for varying the magnitude of the current of said stream.

'5. Superregenerative receiver apparatuscomprising a velocity-modulation oscillation tubeincluding a cathode, 'an `accelerating electrode, a velocity-modulator circuit, an energy-extracting circuit separated from saidmodulator circuit by adrift space, and a detector electrode system positioned beyond said-extracting circuit,'means for maintaining anaccelerating voltage between said cathode and said accelerating electrode,.and an auxiliary oscillator Ycoupled to said tube Ato vary the electronbeam current intensity periodically tointerrupt the oscillations of said tube.

'6. Superregenerative `receiver apparatus vcomprising means for producing an electron stream, a cavityresonator means positioned to receive and interact with said stream to produce high frequency oscillations, detecting means positioned in the path of said stream and responsive to the amplitude of said oscillations, and means for periodically quenching said oscillations.

7. High frequency object detecting apparatus comprising an electromagnetic oscillator, detector means for indicating the oscillating condition of said oscillator, means coupled to said oscillator for transmitting radiation therefrom toward a distant object and for receiving radiation reflected .by said distant object, means for alternately andfregularly changing the vcondition of said oscillator from a sensitive detecting condition to an eicient oscillating condition,- and an alternating-current circuit coupled to said detector means whereby thev frequency of excitation of said circuit indicates the velocity of approach or recession of said object toward or away from said apparatus.

8. High frequency object detecting apparatus, comprising means Vfor producing an electron stream, means for varying the velocity ofthe electrons of said stream, receiving means coupled to said velocity-varying means, means forextracting high frequency energy fromsaid--veloeity-varied electron stream, transmitting means coupled to said extracting means, means interconnecting said extracting and varying means whereby self-excited oscillations are produced in said transmitting means, and means forcausing said extracting circuit to oscillate alternately with strong and Weak oscillations, whereby said apparatus is adapted tov alternately serve as a sensitive detector of waves radiated by said transmitting means and reilected from a distant object and as an eicient oscillator to transmit said radiations.

9. High frequency apparatus comprising means for producing an electron stream, means responsive to received energy for periodically varying the current of said electron stream, means for extracting high frequency energy from` `said varied stream, means interconnecting said extracting andV varying means whereby self-excited oscillations are produced in said extracting means, means for radiating ajportion of'said extracted energy, and means for causing said extracting circuit to oscillate alternately with strong and weak oscillations, whereby said'apparatus is adapted to serve alternately as `an eicientoscillator to transmit radiations and as a sensitive oscillating detector of radiations 'reected from a distant object.

10. In a device of the characterdescribed, an oscillator having antennae means for radiating and Vreceiving electromagneticenergy, said oscillator lhaving means for setting up an4 exciting electron stream for establishing Oscillations of limited amplitude therein to operatev the -device as a sensitive receiver, the amplitude of said oscillations being determined by the amplitude of energy received thereby, additional oscillator means ,for cyclically varying the electron stream current for increasing the amplitude of oscillation of said oscillator at cyclically regular intervals to operate the device as an efficient transmitter of electromagnetic, radiation, whereby a portion of the energy transmitted while the de-V vice is an efficient transmitter may be received by reflection from a remote object while -tl''e device is operating as an eiiicient receiver,l and' a detector responsive to changes in amplitude' of oscillation of said oscillator.'

ll. High frequency apparatus comprising an oscillator having means for radiating and receiving electromagnetic energy, means for causing said oscillator to operate with oscillations of limited amplitude whereby said oscillator is adapted to operate as an eiiicient receiver of electromagnetic radiation, the amplitude of oscillation as a receiver being determined by the amplitude of energy received thereby, means for periodically increasing the amplitude of oscillation of said oscillator whereby said oscillator is adapted to operate as an e'lcient transmitter of electromagnetic radiation, and a detector responl1 sive to changes in amplitude of oscillation of said oscillator, whereby a portion of the energy transmitted while the device is an efficient oscillator and received by reflection from a remote object While the device is operating as an efficient receiver will indicate the presence of said object.

12. Ultra high frequency apparatus comprising a resonator, means for producing first and second streams of electrons and directing said electron streams through said resonator, means including said last-named means for producing ultra-high frequency oscillations in said resonator, and means for regularly quenching the oscillations in said resonator, said last-named means comprising means for modulating said second electron stream at the frequency of said oscillations and in phase opposition to said oscillations.

13. Ultra high frequency apparatus comprising rst and second aligned resonators, means for directing an electron stream through said first and second resonators, said first resonator including means for imparting velocity modulation to the electrons of said stream, said second resonator including means for deriving oscillatory energy from said stream, said means included in said second resonator being spaced an appreciable distance from said means included in said rst resonator whereby said velocity modulation results in arrival of said electrons at said second resonator in bunches, means for providing regenerative feedback from said second resonator to said first resonator for rendering said apparatus self-oscillatory, means for periodically interrupting the oscillations in said rst and second resonators at a frequency appreciably lower than the resonant frequency of oscillations in said resonators, means for injecting Weak oscillatory signals into one of said resonators, and means responsive to average strength of oscillations in one of said resonators for detecting variations therein according to variations of the injected Weak signals.

14. Ultra high frequency apparatus as defined in claim 13, further including means coupled to said second resonator for radiating energy therefrom at predetermined intervals.

15. Radio object detection apparatus comprising a velocity modulation oscillator including a cavity resonator, means for supplying thereto direct current power to produce oscillations in said resonator, means for directionally radiating an appreciable part of the energy produced therein, and for introducing therein high frequency energy reflected back from distant objects, and means for rendering said velocity modulation oscillator alternately oscillatory and quiescent.

16. Radio object detection apparatus as defined in claim 15, including means responsive to variations of strength of oscillations in said velocity modulation oscillator for detecting varia- 12 tions of average strength of the energy reflected back from distant objects.

17. Ultra high frequency apparatus comprising a velocity modulation oscillation generator including a resonator, means for producing an electron stream and directing it through said resonator, means cooperating with said electron stream producing means and said resonator for imparting velocity modulation to said electron stream for providing ultra high frequency energy-yielding bunches therein for energizing said resonator; and means modulating said generator at a frequency appreciably lower than the resonant frequency of said resonator for rendering said generator alternately oscillatory and quiescent, said last-named means including a degenerative feedback quenching circuit acting upon said resonator in response to said modulating means for recurrently dynamically damping out the oscillatory energy in said resonator at a repetition frequency equal to said appreciably lower frequency.

18. Superregenerative receiver apparatus comprising a velocity modulation oscillator including first and second cavity resonators, feedback coupling means between said second resonator and said rst resonator, means for producing a stream of electrons and directing said electron stream through said rst and second cavity resonators to produce high frequency oscillations therein, means for periodically interrupting the high frequency oscillations therein, means for injecting oscillatory signals into one of said resonators, and means responsive to the average strength of oscillations `in said resonators.

OLIVE D. ROSS. Execatri of the Estate of William W. Hansen,

Deceased.

RUSSELL H. VARIAN. SIGURD F. VARIAN.

REFERENCES CITED The following references are of record in the le of this patent:

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